1 /* 2 * Copyright (C) 2017 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #ifndef NETD_SERVER_NETLINK_UTIL_H 18 #define NETD_SERVER_NETLINK_UTIL_H 19 20 #include <functional> 21 #include <linux/netlink.h> 22 #include <linux/rtnetlink.h> 23 24 #include "NetdConstants.h" 25 26 namespace android { 27 namespace net { 28 29 const sockaddr_nl KERNEL_NLADDR = {AF_NETLINK, 0, 0, 0}; 30 31 const uint16_t NETLINK_REQUEST_FLAGS = NLM_F_REQUEST | NLM_F_ACK; 32 const uint16_t NETLINK_ROUTE_CREATE_FLAGS = NETLINK_REQUEST_FLAGS | NLM_F_CREATE | NLM_F_EXCL; 33 // Don't create rules with NLM_F_EXCL, because operations such as changing network permissions rely 34 // on make-before-break. The kernel did not complain about duplicate rules until ~4.9, at which 35 // point it started returning EEXIST. See for example b/69607866 . We can't just ignore the EEXIST 36 // because if we hit it, the rule was not created, but we will think it was, and we'll then trip up 37 // trying to delete it. 38 const uint16_t NETLINK_RULE_CREATE_FLAGS = NETLINK_REQUEST_FLAGS | NLM_F_CREATE; 39 const uint16_t NETLINK_DUMP_FLAGS = NLM_F_REQUEST | NLM_F_DUMP; 40 41 // Generic code for processing netlink dumps. 42 const int kNetlinkDumpBufferSize = 8192; 43 typedef std::function<void(nlmsghdr *)> NetlinkDumpCallback; 44 typedef std::function<bool(nlmsghdr *)> NetlinkDumpFilter; 45 46 // Opens an RTNetlink socket and connects it to the kernel. 47 WARN_UNUSED_RESULT int openNetlinkSocket(int protocol); 48 49 // Receives a netlink ACK. Returns 0 if the command succeeded or negative errno if the command 50 // failed or receiving the ACK failed. 51 WARN_UNUSED_RESULT int recvNetlinkAck(int sock); 52 53 // Sends a netlink request and possibly expects an ACK. The first element of iov should be null and 54 // will be set to the netlink message headerheader. The subsequent elements are the contents of the 55 // request. 56 57 // Disable optimizations in ASan build. 58 // ASan reports an out-of-bounds 32-bit(!) access in the first loop of the 59 // function (over iov[]). 60 #ifdef __clang__ 61 #if __has_feature(address_sanitizer) 62 __attribute__((optnone)) 63 #endif 64 #endif 65 WARN_UNUSED_RESULT int sendNetlinkRequest(uint16_t action, uint16_t flags, iovec* iov, int iovlen, 66 const NetlinkDumpCallback *callback); 67 68 // Processes a netlink dump, passing every message to the specified |callback|. 69 WARN_UNUSED_RESULT int processNetlinkDump(int sock, const NetlinkDumpCallback& callback); 70 71 // Flushes netlink objects that take an rtmsg structure (FIB rules, routes...). |getAction| and 72 // |deleteAction| specify the netlink message types, e.g., RTM_GETRULE and RTM_DELRULE. 73 // |shouldDelete| specifies whether a given object should be deleted or not. |what| is a 74 // human-readable name for the objects being flushed, e.g. "rules". 75 WARN_UNUSED_RESULT int rtNetlinkFlush(uint16_t getAction, uint16_t deleteAction, 76 const char *what, const NetlinkDumpFilter& shouldDelete); 77 78 // Returns the value of the specific __u32 attribute, or 0 if the attribute was not present. 79 uint32_t getRtmU32Attribute(const nlmsghdr *nlh, int attribute); 80 81 } // namespace net 82 } // namespace android 83 84 #endif // NETD_SERVER_NETLINK_UTIL_H 85
